07.00-03 Knot Tying
Any description makes knot tying sound more difficult than it actually is. Do not be discouraged if you find it difficult at first - almost everybody does. The best way to develop a dependable technique for tying safe, reliable knots is repeated practice of the processes covered in this module.
You will learn how to tie a reef knot, surgeon's knot and Aberdeen knot, as well as how to tie at depth and in a confined space.
In this module
07.01 The Reef Knot
The standard knot used in routine surgery is the reef knot, sometimes called the square knot. The reef knot is ideal for most purposes. It is symmetrical, lies flat and gets tighter when the ends are pulled.
An instrument tied reef knot is generally recommended when closing a skin wound with sutures. This allows you to control suture tension with great precision without wasting suture material.
The knot has two components - a direction of throw and a direction of pull. Both components must be changed as you make the knot. Otherwise you will form a granny knot which will slip.
A single reef knot is not sufficient. Build up at least three throws, each forming a reef knot with the one before. Five throws are enough, even for smooth monofilament which is springy and can be difficult to tie.
Although this method consumes more suture material, there will be occasions when you will need to tie your knot by hand to achieve the best result.
07.02 Instrument Tied Reef Knot
An instrument tied reef knot is recommended when closing a skin wound with sutures, provided that the wound is not subjected to strong tension.
Using a needle-holder for tying allows you to place the sutures precisely and control the tightness of the knot.
07.02.01 Principles
Making your reef knot involves two stages. Each stage has two components - a direction of throw and a direction of pull. Both components must be changed as you make the knot.
After looping the blue suture end once forward around the needle holder, the jaws pick up the free suture end (here coloured green) and the throw is pulled flat. The blue suture is then looped once around the needle holder in the opposite direction, and the direction of pull is also reversed to ensure that the whole knot lies flat when tightened.
07.02.02 Instrument Tie on Knot Tying Trainer
In this demonstration, the white end of the thread represents the free end of the suture and the red represents the end attached to the needle.
For the first throw, the red suture end is looped once forward around the needle holder. The needle holder then picks up the white suture end and brings it back through the loop. The hands pull apart to make the knot lie flat. This completes the first throw.
For the second throw, the red end is looped once around the needle holder in the opposite direction to the first throw, and the hands also pull apart in opposite directions.
For the third throw, again the direction of throw and pull are reversed.
The whole knot lies flat when tightened.
07.02.03 Assembling Your Knot Tying Trainer
You will use the sucker feet from the skin pad jig as the anchor points for this kit, so remove them from the underside of it.
Make sure that the sucker feet will be properly oriented and comfortably positioned in front of you before you secure them in place.
Lightly moisten the sucker feet and place them 12 to13cm apart (measuring from the middle of each foot).
Attach the red knot tying band to the top of the sucker feet.
Place the two-coloured knot tying cord under the knot tying band. You are now ready to start practising.
07.02.04 Practise Tying
Start by placing your practice thread under the knot trainer strings, with the white end furthest away from you. Hold the red end between your left thumb and index finger and hold your needle holder in your right hand.
Wrap the red thread over the needle holder and away from you to form a loop. Pick up the white end with the needle holder and bring it through the loop towards you, whilst simultaneously pushing the red thread in your left hand away from you. Pull your hands apart to tighten. This completes the first throw.
For the second throw, bring the red thread in your left hand back towards you and place the needle holder under it. Wrap the red thread around the needle holder in the opposite direction to last time, i.e. by bringing it towards you. Pick up the white end with the needle holder, take it through the loop and away from you, whilst simultaneously bringing the red thread in your left hand towards you. Pull your hands apart to tighten. This completes the second throw.
Make a third throw in exactly the same way as the first. Wrap the red thread over the needle holder and away from you to form a loop. Pick up the white end with the needle holder and bring it through the loop towards you, whilst simultaneously pushing the red thread in your left hand away from you. Pull your hands apart to tighten. Ensure that the whole knot lies flat when tightened.
07.03 Hand Tied Reef Knot
Although this is more wasteful of suture material, a hand tied reef knot can be useful when you are tying under a lot of tension, for example when inserting sutures deep to the skin and when tying ligatures. It allows you to hold both suture strands under tension and to control slippage.
07.03.01 Principles Video 1
The knot is predominantly constructed with one hand, which forms a loop through which the free suture end is passed. The other hand is used to hold the free suture end.
The throws are made with the index finger and middle finger alternately.
In this video we show the right hand forming the knots, but it is equally acceptable to use the left.
07.03.02 Principles Video 2
Just as with an instrument tied reef knot, in order to form a safe and correct knot you must change the direction of throw and pull at each stage.
If, as shown here, you throw the knot and pull the hands apart without crossing them over, the knot does not lie flat and is incorrect. To make it lie flat, your hands should cross over, so that they are diametrically opposite where they started, and then pull away from each other. The knot is now flat and correct. However, when operating it is awkward and impractical to cross the hands and by doing so you will impede the view of the site you are working on.
For your first throw, a way to avoid this is to cross the threads before you begin. Now, when making the first throw, the hands can stay on the sides where they started and pull apart to make a flat, safe knot. This method should only be used for the first throw.
For subsequent throws, however, you still want to avoid impeding the view of the operative site when you cross your hands over. A compromise is still to alternate the position of your hands but just to move them at right angles rather than fully crossing them over. The resulting throws will be more or less flat and the finished knot will be safe because the first throw was correctly formed.
In our practice video we show the right hand forming the knots. Once you have mastered this technique, you may want to try using your left hand as this will allow you to keep hold of the needle holder in your right and improve suturing efficiency.
07.03.03 Practice Video 1
Place the practise thread under the knot trainer strings with the white end to the left, then cross the two ends over the top of the trainer strings so that the red end is on the left and the white on the right. This will avoid you having to cross your hands over when tightening the first throw.
Hold the white end between your right thumb and middle finger and the red end between your left thumb and index finger. Use your extended right index finger to push the white thread over and across the red thread, creating some tension. Take the tip of your right index finger down through the loop then bring it back towards you to hook the white thread around it. Rotate your finger tip to bring the white end back up through the loop and pull it through. Tighten the throw by pulling your hands apart, applying horizontal tension on both strands.
This completes the first throw.
07.03.04 Practice Video 2
For the second throw, hold the white end between your right thumb and index finger and use your middle finger to make the throw.
To tighten, rotate your hands by 90 degrees so that you are pulling the left (red) thread towards you and the right (white) away from you.
In a surgical setting you would snug the throw down tightly with your finger, but to make it easy to unpick your knot and practise again we advise you to do this gently.
For the third throw, repeat what you did for the first. Holding the white end between your right thumb and middle finger, use your extended right index finger to make the throw.
To tighten, rotate your hands by 90 degrees in the opposite direction to the last throw, and pull the left (red) thread away from you and the right (white) thread towards you.
Snug the knot down with your finger to tighten.